This paper introduces a spiral guidance law for intercepting missiles or satellites. The law is termed spiral because it directs the kill vehicle (KV) along a spiral-shape trajectory. The guidance law has two important features: (1) it directs the KV along a trajectory that makes target range observable to an angle-only (passive) sensor, and (2) it does not require the KV's thrust to be throttled. The second feature permits the use of divert motors that burn at a fixed predetermined rate, such as fixed-impulse solid-fuel divert motors.